Various types of exchange columns in which a gas and a liquid come into contact with one another for purposes of mass or heat transfer, fractionation and or separation of feed stock constituents, and other unit operations are known in the art. Counter-current flow of vapor and liquid within such exchange columns have become established methods of vapor-liquid contact. The actual vapor-liquid interface requires the use of distillation trays or a packing bed within the column. Liquid is distributed above the trays or packing bed while vapor is distributed beneath the tray or packing bed. Liquid descend upon a tray or trickling downwardly through the packing bed is exposed to the vapor ascending upwardly for vapor-liquid contact and interaction.
The configuration of the column internals determines the efficiency of the vapor-liquid interface and the concomitant mass and energy transfer occurring in a process tower. Effective and even distribution of the vapor and the liquid on opposite sides of the distillation tray or packing bed creating homogeneous mixing zones are also critical to an efficient operation. Uneven liquid distribution can lead to poor contact and mass transfer between ascending vapor streams and descending liquid streams. With efficiency being readily convertible to cost of operation and production quality, many designs exist today. However, the efficiency of the column can be limited by the efficiency of the vapor and liquid distribution across the column internals. For example, should either vapor or liquid fail to evenly distribute over a portion of distillation tray or packing bed, that portion will not be used to its full potential thus decreasing the efficiency and cost effectiveness of the operation. Therefore, aside from the trays and packing beds themselves, the liquid distributor is the most important unit of a tower internal. Failure in performance of a tower sometimes stems from liquid distribution problems such as clogging or uneven distribution.
When using packing beds, efficiency can be lost through small regions of non-homogenous interaction between the vapor and liquid. Many high efficiency packing designs require counter-current vapor-liquid flow through channels defined by opposed corrugations of sheets. If the initial liquid or gas distribution fails to enter a particular corrugation pattern, then precious surface area is lost in the packing until the liquid and vapor are urged to migrate into and interact through the unfilled regions of the packing. The result is poor efficiency. Better liquid distribution across the packing would reduce the problem, and to achieve better liquid distribution across the packing it is desirable to increase the uniform distribution of liquid of a parting box which in turn feeds a packed bed distributor. If the liquid entering a column is distributed more uniformly across each section of a parting box, each section of the parting box is able to deliver a more uniform liquid feed to a packed bed distributor. The novel liquid distributor of the present invention is able to function as a parting box feeding the correct amount of liquid in a uniform distribution to a packed bed distributor.
Although many prior art systems, such as spray orifices, pipes, perforated plates, apertured troughs and nozzles, are generally effective in distributing some vapor and some liquid to most portions of a tray or packed bed distribution system, uniform distribution is usually not obtained without a more sophisticated distribution apparatus. For example, simply spraying liquid on top of the tray often results in high concentrations of liquid flow in certain portions of the tray and less flow in others. Orifice distributors are generally susceptible to plugging, leading to uneven irrigation within the tower. Surface irregularities in a distributor pan occurring during manufacture likewise increase flow resistance of some perforations or induce liquid flow along the bottom of the pan which is a distinct disadvantage. Overall, any flow irregularity which focuses the flow in one area while reducing flow in other areas is deleterious to the efficiency of the operation.
It would be an advantage, to provide an assembly for even and uniform liquid distribution of the liquid onto a tray. Examples of previous designs include U.S. Pat. Nos. 6,722,639 and 4,729,857. U.S. Pat. No. 4,729,857 teaches a liquid flow distributor with a plurality of troughs formed with a downwardly tapering body section having holes formed therein for spewing liquid outwardly there from. Baffles are disposed outwardly of the lower tapering body sections of the trough for receiving the spew of liquid there from and evenly distributing the liquid flow downwardly. U.S. Pat. No. 6,722,639 teaches a liquid distributor that includes a plurality of elongated troughs that are spaced apart and extend across the column. A plurality of liquid discharge holes are positioned in side walls of the trough and are located in one or more pre-selected planes that are preferably spaced above a floor of the trough. Splash baffles are spaced outwardly from the trough side walls and include upper portions that are positioned to receive liquid exiting the troughs through the discharge holes. Lower portions of the splash baffles form a constricted discharge outlet in a plane below the trough for delivering liquid from the splash baffles to the underlying mass transfer bed. The splash baffles are vertically adjustable and are intended to be supported on the upper surface of the mass transfer bed so that the discharged liquid is delivered directly to the mass transfer bed, thereby reducing the opportunity for the falling liquid to become entrained in a vapor stream flowing upwardly through the mass transfer bed.
The present invention provides a novel liquid distribution assembly that is more efficient than those of the art, especially in situations where the velocity of the liquid in the flow pipe is high. In this high efficiency distributor system a uniform flow of liquid is maintained through a flow equalizing system. The apparatus contains a trough with patterned apertures, a perforated v-plate situated within the trough, and a flow pipe disposed above the trough. A preferred embodiment additionally has dividers situated within the perforated v-plate. The apparatus may be used to deliver a uniform distribution of liquid to a distillation tray. In some applications, the apparatus or multiples sets of the apparatus may be used as a parting box to deliver a uniform distribution of liquid to a packed bed distributor.
The flow pipe delivers multiphase liquid to an open trough equipped with discharge apertures, usually arranged in a specific pattern. In some embodiments, multiple flow pipes may deliver the liquid to a network of open troughs. The trough is commonly used in mass transfer columns to receive liquid from an overlying region and redistribute the liquid uniformly to the underlying tray. However, if the flow pipe were to discharge directly into the open trough, liquid would be discharged from the apertures of the trough at non-uniform flow rates. Those apertures directly in alignment with the discharge from the flow pipe might experience a higher flow rate of liquid, which those apertures out of alignment with the flow pipe discharge might experience a lower flow rate of liquid. With the inventive v-plate housed within the trough, the flow rate of the liquid discharging from the flow pipe is disrupted and modified so that the liquid flowing through the perforations of the v-plate and into the trough are more uniform. The homogeneity of the liquid flow rate is increased even further in the embodiment where the perforated v-plate is equipped with dividers. In an alternative embodiment multiple troughs act as a parting box to redistribute the liquid uniformly to a packed bed distributor.